The present invention relates generally to dynamoelectric machines having stator and rotor components and more specifically to a particular construction for said dynamoelectric machines made in order to reduce vibration and noise during machine operation.
A wide variety of dynamoelectric machines having stator and rotor components are already known including machines having rotation or linear motion occurring between said components during operation of a particular machine. Known rotating dynamoelectric machines include both electric motors and electric generators. A wide variety of rotating electric motors is also known, including motors having an outer stator housing with an inner rotating rotor, an inverted motor wherein the stator is positioned within the bore of an outer rotating rotor and the electric motor component for an adjustable speed drive system. In known linear or non-rotating dynamoelectric machines, the rotor or translator component moves in a linear direction with respect to the stator component employed in said machine. The present invention provides a novel means applicable to all said type dynamoelectric machines for reducing the vibration and noise otherwise being encountered during machine operation. More particularly, a novel method and means to modify the structural features of the electromagnetic structure in said dynamoelectric machines is provided according to the present invention which is found to reduce operating vibration and noise. As used herein, the term xe2x80x9celectromagnetic structurexe2x80x9d is defined as the laminations and the electrical conductors of the stator component including all associated devices and materials attached to said stator component construction.
In U.S. Pat. No. 5,861,699 a stator core for an electric machine, such as an electric motor, is described having axial variations in the radial dimensions of the laminations by rotating said laminations with respect to each other for reduced noise. It is further stated therein that such noise attenuation is attributable to such uneven stator lamination construction. There is further disclosed in U.S. Pat. No. 6,191,510 structural means to internally damp the stator component of an electric motor for reduced vibration by inserting viscoelastic damping material between the stator laminations. There still remains need to further reduce the vibration and noise being experienced when operating a dynamoelectric machine. without significantly degrading its electrical performance.
The present provides a method and means for structurally modifying the electromagnetic structure in a dynamoelectric machine after already having been designed for optimum electrical performance. In doing so according to the present invention, resonant vibration and noise can be diminished without significantly degrading the electrical performance. The first step in the present method of reducing vibration and noise is to disorient the maximum receptances of the electromagnetic structure at natural frequencies with respect to the applied magnetic forces at the same frequencies in order to reduce the overall receptance in said structure and thereby reduce its overall response. The term xe2x80x9creceptancexe2x80x9d in said electromagnetic structure is understood to be the ratio of physical displacement response with respect to the applied magnetic force. The term xe2x80x9cresponsexe2x80x9d is understood to be the physical elastic displacement in said electromagnetic structure which can be perceived as vibration and/or noise. The mechanical features of said electromagnetic structure are modified in accordance with such evaluation to reduce any close coincidence between the overall receptance of said modified electromagnetic structure and said applied magnetic force. The remaining step in the present method is the utilization of sites in the electromagnetic structure for damping to further attenuate a diminished vibration response. The principle of xe2x80x9cslip potentialxe2x80x9d is employed as a means for creating sites for slip damping to attenuate undesired resonant amplification of the vibration. In accordance with said latter procedure, adjacent stator laminations in said electromagnetic structure are modified to provide slip damping therebetween due to having dissimilar receptance.